New users not showing as option in "add author" (1 post)

I want to change authors for post and created a custom user on the website — SVA-member. However, when I go to change posts to this user instead of the admin author, it's only showing me users with total admin privileges.

Is there a way to add ALL new users in this list of options for author of posts? I don't want to make them admins, but I'd like to change the authorship of a post to them instead of me.